1. Field of the Invention
The present invention relates to a half tone mask having a transparent substrate, a light semitransmission layer and a light shield layer, a method for fabricating the same, and a flat panel display using the same.
2. Description of the Related Art
A photo mask, which is generally used in patterning using a photolithography process, as shown in FIG. 1, comprises a transparent substrate 11, light transmission portions 13 formed on the transparent substrate 11 for completely transmitting light, and light shield portions 15 formed on the transparent substrate 11 for completely shielding light.
The above conventional mask forms only one pattern layer, thus being used only in one cycle of the photolithography process including exposure, development, and etching. More specifically, in a Thin Film Transistor (TFT) and a Color Filter (CF) of a liquid crystal display, many layers are deposited/applied, and the deposited/applied layers are respectively patterned by the photolithography process. The reduction of only one cycle of the photolithography process results in economic advantages. However, the conventional mask forms only one pattern layer, thus being noneconomical.
In order to solve the above problem, a gray tone mask comprising light transmission portions completely transmitting light, a light shield layer completely shielding light, and a slit pattern transmitting a reduced amount of irradiated light has been developed. However, the gray tone mask controls the amount of light transmission using diffraction of light passing through a fine pattern, thus having a limit in the amount of light transmission due to the limit of the slit pattern. Further, when the gray tone mask has a size more than a designated value, it is not possible to achieve the uniform patterning.